Pressure sores are a significant and common cause of morbidity and mortality in spinal cord injury (SCI) patients. Spinal cord injury (SCI) represents a significant health problem associated with life long disability and a broad range of secondary complications. Approximately 10,000 individuals incur a spinal cord injury in the United Sates each year. The costs of these injuries to both individuals and society are staggering. A recent cross-sectional multi-center study concluded that total direct costs for all cases of SCI are $7.736 billion in the United States (data provided in constant 1995 dollars) In addition, it has been estimated that the direct cost represents only 35% of the total aggregate costs of SCI to society. The remaining 65% are indirect costs associated with lost wages, fringe benefits, productivity, and leisure time.
Pressure related decubital ulcers present one of the most significant secondary complications of spinal cord injury, occurring in 10%-32% of SCI patients. The ischial tuberosity is the most common site for pressure sores, accounting for 28% of all ulcers. As much as 25% of the total cost of caring for spinal cord injury patients is spent on treatment of decubital ulcers. Considering the gradual decline in mortality rates from spinal cord injuries, coupled with an aging population, it is conceivable that the group of patients prone to developing pressure sores will increase in the future. The bulk of the literature to date has primarily focused on the technical aspects of surgical management of pressure sores.
The development of musculocutaneous flaps in the late 1970's revolutionized surgical management of pressure sores. Various musculocutaneous flaps have been used to treat ischial ulcers. However, long-term follow-up of those flaps has demonstrated wide variability in outcome and success rates. Reported recurrence rates of pressure sores repaired using musculocutaneous flaps range from 33%-80%. It is apparent that long-term therapeutic results remain sub-optimal and reliable alternatives in the management of pressure sores are highly desirable.
It is well established that the principle, and often solitary, cause of the decubital ulcers is excessive pressure, usually on a bony prominence in susceptible individuals. Sitting posture naturally creates high contact pressures at both ischial tuberosities, the coccyx, and in some cases the greater trochanters. The magnitude of contact pressure over ischial tuberosities has been found to correlate well with incidence of pressure sores. As a result of immobility and impaired protective sensation, wheelchair-bound SCI patients are at ongoing significant risk of pressure sores in these regions. Recently, various designs of wheel chair cushions have been introduced to relieve high contact pressure at the bony prominences. Ragan et al demonstrate that the highest seat-interface pressure is in the region located within 1 or 2 cm of the ischial tuberosity with maximum compressive stress inferior to the bottom surface of the ischial tuberosity. Some reduction of the pressure was obtained with an 8 cm thick cushion. However, increasing the cushion thickness beyond 8 cm was ineffective in further reducing subcutaneous stress.
Inflatable cushions currently available for wheelchairs have the inherent problems from air leaks, inaccurate adjustment, improper positioning, deterioration of the cushion, as well as over or under inflation. Changes in the inflation of these cushions occur due to leakage of the cushion or in the system, and with changes in temperature or altitude. These problems often result in the formation of sores and ulcers due to pressure points, especially in users with impaired sensation.
In addition, cushions are difficult to adjust, thereby decreasing the users mobility or necessitating assistance. The need for external pumps for inflation further complicates installment and use, and interferes with folding the wheelchair for travel or storage.